Drying device with improved guide for rotary cut wood veneer

ABSTRACT

A device (10) for drying rotary cut wood veneer comprises at least two conveyor loops (11) facing each other along an outbound path to define between them a conveyance passage for the rotary cut veneer. Along the outbound path are present drying means (18) acting on the conveyance passage. The two conveyance loops comprise conveyance chains (13) supporting transversely to the direction of conveyance a sequential jointed plurality of rigid elements (12) providing facing and essentially unbroken conveyance surfaces along said outbound path to delimit the conveyance passage.

BACKGROUND OF THE INVENTION

In the art of wood treatment, rotary cut wood veneer drying plants arewell known.

U.S. Pat. No. 3,199,213 discloses a method for changing the moisturecontent of wood through strong heating and cooling. U.S. Pat. No.3,623,235 shows a drying apparatus for veneers, having a conveyor fortransporting the material through a passage between radiant dryingunits.

EP-A-0 451 346 discloses a dryer comprising hot plates hinged to eachother for forming two caterpillars reciprocally faced to define aconveyance passage for the wood veneer. Devices of this kind have astructure very complex, since drying is carried out by heating fluidcirculating along tubes inside the movable plates. The uniformity ofdrying is very low. Other known plants comprise a conveyance systemmoving the material to be dried under hot air currents.

GB-A-5335 discloses a device for drying slack objects like wet rags,conveyed on supporting plate conveyor through hot air flow. Thesupporting plates have some perforations for the passage of a certainamount of air. The conveying surface is interrupted by flanges bent atright angle on the conveying surface.

A further problem with known drying veneer plants when used for dryingwood veneers is that during drying the veneer undergoes shrinkingphenomena, which must be assisted to avoid cracking and damage to thewood, and deformation phenomena which on the contrary must be preventedas much as possible.

In the prior art there have been proposed plants in which the conveyancesystem is provided by a sequence of motorised rollers parallel with eachother to be coupled on both sides of the rotary cut veneer. This permitsthe rotary cut veneer to run while assisting shrinkage. To allow passageof hot air it is however necessary to leave ample spaces between theroller pairs along the rotary cut veneer path. Between one pair and thenext the rotary cut veneer can thus be deformed. The leading edge of therotary cut veneer can also deviate from the established path and fitinto the space between two pairs of rollers to jam the machine.

In some machines guide belts have been added and arranged to run betweenthe rollers so as to guide the rotary cut veneer between one roller pairand the next. Because of its flexibility the guide belts cannot howeverprevent deformation of the rotary cut veneer along the path between therollers.

There have also been proposed machines in which a chain system moves aplurality of equally spaced crosspieces arranged on either side of therotary cut veneer to conduct it along the drying path. Even in this casedeformation of the rotary cut veneer between two successive supports isnot prevented.

The general purpose of the present invention is to overcome the aboveshortcomings by supplying a rotary cut wood veneer drying machinepermitting perfect guidance of the rotary cut veneer and allowing freeshrinking but preventing any deformation.

SUMMARY OF THE INVENTION

In view of said purpose it was sought to provide in accordance with thepresent invention a device for drying rotary cut wood veneer andcomprising at least two conveyor loops facing each other along anoutbound path to define between them a conveyance passage for the rotarycut veneer with there being along the outbound path drying means actingon the conveyance passage and characterized in that the two conveyanceloops comprise conveyance chains supporting transversely to thedirection of conveyance a sequential jointed plurality of rigid elementsproviding facing and essentially unbroken conveyance surfaces along saidoutbound path to delimit the conveyance passage.

BRIEF DESCRIPTION OF THE DRAWINGS

To clarify the explanation of the innovative principles of the presentinvention and its advantages compared with the prior art there isdescribed below with the aid of the annexed drawings a possibleembodiment thereof by way of non-limiting example applying saidprinciples. In the

FIG. 1 shows a schematic side view of drier in accordance with thepresent invention, and

FIG. 2 shows a schematic perspective view of a part of the drier of FIG.1.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures, FIG. 1 shows schematically a drierindicated as a whole by reference number 10 and comprising at least twomotorised conveyor loops 11 facing each other along an outbound sectionalong which are present drying means provided by devices 18 for hot airemission and moisture removal essentially of the prior art and which acton a rotary cut veneer sheet conveyed by the conveyors 11 in the spacebetween the two facing sections.

In accordance with the present invention, along the outbound path theconveyors 11 define a conveyance passage for the rotary cut veneerdelimited by a sequential jointed plurality of rigid elements 12 whichprovide facing and essentially unbroken handling surfaces along theoutbound path as may be seen in FIG. 1.

The elements 12 are supported along handling chains 13 coupled at thetwo lateral ends of the rigid elements 12. Advantageously each rigidelement is supported at its opposite ends by a pair of carriages 14 witheach carriage of the pair running at least along the outbound path alongcorresponding guides. Advantageously each carriage 14 forms a link of ahandling chain.

To keep a predetermined distance between the superimposed surfacesdefined by the mobile elements the lower conveyor carriages are at leastrested on a rail 15 while the upper conveyor carriages are guided insupport on a first lower rail 16 and have their vertical movementprevented by a second upper rail 17.

As may be seen in FIG. 2 the rigid elements 12 are provided in generallyrectangular form extending transversely to the direction of motion ofthe conveyor chains and are pierced to permit passage of air between thedrying means 18 arranged on one side thereof and the conveyance passageon the other side.

To preserve an essential rigidity of each element 12 and prevent bendingthereof even in the case of high extensions transverse to the path ofmovement, between each pair of carriages 14 is arranged a crosspiece 19supporting the rigid element having generally the form of the letter T.

It is now clear that the preset purposes have been achieved. In theconveyance path of the rotary cut veneer the rotary cut veneer is guidedbetween essentially rigid and unbroken surfaces made up of the rigidelements 12. Thus any deformation transverse to the direction of motionof the rotary cut veneer is prevented.

But at the same time a sliding of the rotary cut veneer caused byshrinking due to the drying operation is permitted.

By appropriately adjusting the distance between the carriage guides itis also possible to adjust the distance between the facing conveyancesurfaces so as to have a predetermined pressure on the rotary cut veneerpassing through the conveyance and drying passage.

Naturally the above description of an embodiment applying the innovativeprinciples of the present invention is given merely by way of exampleand therefore is not to be taken as a iimitation of the patent rightclaimed here. For example, the drier can be made up of multiple elements10 superimposed so as to provided a plurality of drying paths.

In addition the conveyor chain structure could be different from thatshown schematically as is readily imaginable to those skilled in theart.

I claim:
 1. Device (10) for drying rotary cut wood veneer comprising atleast two conveyor loops (11) facing each other along an outbound pathto define between them a conveyance passage for the rotary cut veneerwith there being along the outbound path drying means (18) acting on theconveyance passage by means of hot air flow, characterized in that thetwo conveyance loops comprise handling chains (13) supportingtransversely to the direction of conveyance a sequential jointedplurality of rigid guidance elements (12) providing facing andessentially unbroken conveyance surfaces along said outbound path todelimit the conveyance passage, preventing deformation of the rotary cutwood veneer transverse to the direction of motion, the rigid guidanceelements (12) being pierced to permit passage of air between the dryingmeans (18) arranged on one side thereof and the conveyance passage onthe other side.
 2. Device in accordance with claim 1 characterized inthat at least along the outbound path each rigid guidance element (12),provided in a generally rectangular form, is supported at its opposingends by a pair of carriages (14) running along guides (15, 16, 17)arranged along said path.
 3. Device in accordance with claim 2characterized in that each carriage (14) makes up a link of a conveyancechain.
 4. Device in accordance with claim 2 characterized in thatbetween each pair of carriages (14) is arranged a crosspiece (19)supporting the rigid guidance element (12) with a T conformation.